This project will study the maternal behavior of the rabbit. This animal has a unique pattern of maternal behavior in which it nurses its young once daily for a brief period. Other components consist of prepartum nestbuilding and hair loosening, postpartum nest defense, nipple pheromone production, and chin marking. Previous work has established that the hormonal basis of nestbuilding, the only maternal behavior studied, is the ovarian hormones estradiol and progesterone and the pituitary hormone prolactin. We propose to study these hormones for their effects on other components of maternal behavior and to determine the role of each of them and their interrelationships. We will also study the role of oxytocin. The second part of this application describes studies aimed at determining the basis for the maintenance of maternal behavior, in view of the brief daily contact between the mother and her young. We will attempt to separate the effects of the sensory and the hormonal stimulation that the female receives during pup contact, chiefly that which occurs during suckling by the young. Evidence suggests that females are more dependent upon pup stimulation (suckling) early postpartum than later. Our guiding hypothesis is that early maternal behavior is initiated and maintained by hormonal stimulation and later maternal behavior is maintained chiefly by stimuli provided by the young.